Re: ONLINE INDEX CREATION
Date: Fri, 14 Sep 2018 06:53:28 +0000
Message-ID: <CWXP265MB1493CEF12F4F397DD0767EF8A5190_at_CWXP265MB1493.GBRP265.PROD.OUTLOOK.COM>
Ramsankar,
It's always a little difficult to work out exactly why things appear to be misbehaving without having all the details in front of you - and it's not always easy to know what details to ask for. The full execution plan - including the "parallel" and "partitioned" columns would probably help. The parallel would show us any P->P, S->P etc distribution.
Given the "45 minutes then it went parallel" sounds like you're doing the tablescan serially and using parallel slaves to create the index. But maybe that's because you're asking Oracle to create a parallel index, not to run the create index as a parallel statement.
Two Options - I'd be interested in know if either, or both, work.
I don't really want to try modelling what your doing because there are so many parallel parameters that produce very different effects, and one effect would be parallelism not appearing for very small objects, another would be the degree and behaviour varying with the number of populated partitions (and their current stats).
Regards
Regards
Hi Jonathan
Thanks for the response. So I noticed that after running for about 45 minutes or so, it started using parallel processing. This is in both cases, PARALLEL with and without ONLINE. However, all of the parallel slaves are waiting on "PX Deq: Execution Msg".
Could this be a BUG?
SQL> list
Jonathan Lewis
Jonathan Lewis
From: Ramsankar Cheruvattath <ram.cheruvattath_at_gmail.com>
Sent: 13 September 2018 19:43:39
To: Jonathan Lewis
Cc: andysayer_at_gmail.com; Oracle Mailing List
Subject: Re: ONLINE INDEX CREATION
1 SELECT QCSID, SID, INST_ID "Inst", SERVER_GROUP "Group", SERVER_SET "Set",
2 DEGREE "Degree", REQ_DEGREE "Req Degree"
3* FROM GV$PX_SESSION ORDER BY QCSID, QCINST_ID, SERVER_GROUP, SERVER_SET
SQL> /
QCSID SID Inst Group Set Degree Req Degree
---------- ---------- ---------- ---------- ---------- ---------- ----------
997 2465 1 1 1 2 2
997 3865 2 1 1 2 2
997 997 1
1038 2803 1 1 1 64 64
1038 2817 1 1 1 64 64
1038 2494 1 1 1 64 64
1038 2858 1 1 1 64 64
1038 2873 1 1 1 64 64
1038 2885 1 1 1 64 64
1038 2901 1 1 1 64 64
1038 2913 1 1 1 64 64
1038 2929 1 1 1 64 64
1038 2943 1 1 1 64 64
1038 2958 1 1 1 64 64
1038 2969 1 1 1 64 64
1038 2997 1 1 1 64 64
1038 3026 1 1 1 64 64
1038 3040 1 1 1 64 64
1038 3054 1 1 1 64 64
1038 3096 1 1 1 64 64
1038 3124 1 1 1 64 64
1038 3166 1 1 1 64 64
1038 3223 1 1 1 64 64
1038 3249 1 1 1 64 64
1038 3278 1 1 1 64 64
1038 3305 1 1 1 64 64
1038 3334 1 1 1 64 64
1038 3376 1 1 1 64 64
1038 3404 1 1 1 64 64
1038 3434 1 1 1 64 64
1038 3473 1 1 1 64 64
1038 3488 1 1 1 64 64
1038 3516 1 1 1 64 64
1038 3544 1 1 1 64 64
1038 3557 1 1 1 64 64
1038 2438 1 1 1 64 64
1038 2466 1 1 1 64 64
1038 2480 1 1 1 64 64
1038 2326 1 1 1 64 64
1038 2493 1 1 1 64 64
1038 2508 1 1 1 64 64
1038 2535 1 1 1 64 64
1038 2522 1 1 1 64 64
1038 2565 1 1 1 64 64
1038 2606 1 1 1 64 64
1038 2620 1 1 1 64 64
1038 2634 1 1 1 64 64
1038 2578 1 1 1 64 64
1038 2648 1 1 1 64 64
1038 2703 1 1 1 64 64
1038 2718 1 1 1 64 64
1038 2732 1 1 1 64 64
1038 2760 1 1 1 64 64
1038 2789 1 1 1 64 64
1038 2801 1 1 1 64 64
1038 2816 1 1 1 64 64
1038 2845 1 1 1 64 64
1038 2857 1 1 1 64 64
1038 2871 1 1 1 64 64
1038 2886 1 1 1 64 64
1038 2914 1 1 1 64 64
1038 2928 1 1 1 64 64
1038 2941 1 1 1 64 64
1038 2312 1 1 1 64 64
1038 2970 1 1 1 64 64
1038 2984 1 1 1 64 64
1038 2745 1 1 1 64 64
1038 1038 1
Ramsankar Cheruvattath (Ram)
4072096276
On Thu, Sep 13, 2018 at 2:21 PM Jonathan Lewis <jonathan_at_jlcomp.demon.co.uk<mailto:jonathan_at_jlcomp.demon.co.uk>> wrote:
The fact that your A-rows for the partition table scans shows zero (on allstats last) suggests that you've got parallel execution slaves executing the tablescans. For parallel queries you shouldn't use LAST as the last thing to execute the statement is the query coordinator. If the 2 minutes and 9 seconds is to be trusted it seems likely that you got some parallelism somewhere. How are you checking ? Your output doesn't tell us much when you don't show us how you're querying - but shouldn't you be looking for the QC_% columns in ASH to check whether your statement ran parallel ?
Regards
Jonathan Lewis
From: oracle-l-bounce_at_freelists.org<mailto:oracle-l-bounce_at_freelists.org> <oracle-l-bounce_at_freelists.org<mailto:oracle-l-bounce_at_freelists.org>> on behalf of Ramsankar Cheruvattath <ram.cheruvattath_at_gmail.com<mailto:ram.cheruvattath_at_gmail.com>> Sent: 13 September 2018 18:31:34
To: andysayer_at_gmail.com<mailto:andysayer_at_gmail.com> Cc: Oracle Mailing List
Subject: Re: ONLINE INDEX CREATION
Enter value for sql_id: cwqxdrvryzjrv
Enter value for child: 0
old 1: select * from TABLE(dbms_xplan.display_cursor('&SQL_ID', &CHILD, format=>'ALLSTATS LAST +outline'))
new 1: select * from TABLE(dbms_xplan.display_cursor('cwqxdrvryzjrv', 0, format=>'ALLSTATS LAST +outline'))
PLAN_TABLE_OUTPUT
SQL_ID cwqxdrvryzjrv, child number 0
CREATE INDEX USER1.BI_ADD_FAILED_PIECE_SCAN_D_I7 ON USER1.BI_ADD_FAILED_PIECE_SCAN_DLY(ORGN_FAC_SEQ_ID, DESTN_FAC_SEQ_ID, ORGN_FAC_ZIP_3) INITRANS 10 NOLOGGING PARALLEL 64 LOCAL COMPRESS 3 Plan hash value: 3405290185
| Id | Operation | Name | Starts | E-Rows | A-Rows | A-Time | Buffers | -----------------------------------------------------------------------------------------------------------------------------
| 0 | CREATE INDEX STATEMENT | | 0 | | 0 |00:00:00.01 | 0 |
| 1 | PX COORDINATOR | | 0 | | 0 |00:00:00.01 | 0 |
| 2 | PX SEND QC (RANDOM) | :TQ10000 | 0 | 4256K| 0 |00:00:00.01 | 0 |
| 3 | PX PARTITION LIST ALL | | 1 | 4256K| 2005 |00:02:09.31 | 24042 |
| 4 | INDEX BUILD NON UNIQUE (LOCAL)| BI_ADD_FAILED_PIECE_SCAN_D_I7 | 2005 | | 2005 |00:00:00.64 | 24042 |
| 5 | SORT CREATE INDEX | | 2005 | 4256K| 0 |00:00:00.63 | 24042 |
| 6 | TABLE ACCESS FULL | BI_ADD_FAILED_PIECE_SCAN_DLY | 2005 | 4256K| 0 |00:00:00.62 | 24042 |
-----------------------------------------------------------------------------------------------------------------------------
Note
- Degree of Parallelism is 64 because of table property
- estimated index size: 272G bytes
25 rows selected.
SQL> _at_racsys
ID SID SERIAL# USERNAME LOGON_TIME ELP_MT SQL_EXEC_START SPID SQL_ID CHD EVENT MODULE SERVICE_NAME STATE WAIT_TIME_SEC PROGRAM
--- ------ ---------- ---------- --------------- ------ --------------------- -------- ------------- ---- ------------------------- ------------------------------ ------------ ---------- ------------- ------------------------------
1 1038 53781 SYS 13-SEP-18 11:05 72 13-SEP-18 11:05 182996 cwqxdrvryzjrv 0 On CPU / runqueue sqlplus_at_HOST1 (TNS SYS$USERS WAITED 0 sqlplus_at_HOST1 (TNS
V1-V3) SHORT TIME V1-V3)
SQL> _at_ashhistory
Enter value for sid: 1038
Enter value for serial: 53781
Enter value for inst_id: 1
old 3: WHERE SESSION_ID=&SID and SESSION_SERIAL#=&serial and inst_id=&inst_id
new 3: WHERE SESSION_ID=1038 and SESSION_SERIAL#=53781 and inst_id=1
Enter value for minute: 72
old 4: and SAMPLE_TIME>=(sysdate-&minute/(24*60))
new 4: and SAMPLE_TIME>=(sysdate-72/(24*60))
SQL_ID EVENT SECONDS
------------- --------------------------------------------- ----------
cwqxdrvryzjrv gc current block 2-way 1
gc current grant busy 1
enq: TS - contention 5
enq: FB - contention 12
enq: HW - contention 14
gc current grant 2-way 33
row cache lock 59
enq: IV - contention 283
On CPU 3860
4268
10 rows selected.
Thanks
Ramsankar Cheruvattath (Ram)
4072096276
On Thu, Sep 13, 2018 at 12:54 PM Ramsankar Cheruvattath <ram.cheruvattath_at_gmail.com<mailto:ram.cheruvattath_at_gmail.com><mailto:ram.cheruvattath_at_gmail.com<mailto:ram.cheruvattath_at_gmail.com>>> wrote: Thanks Andrew! I already checked parallel query servers availability. There were plenty available, but it was not using it.
Thanks
Ramsankar Cheruvattath (Ram)
4072096276
On Thu, Sep 13, 2018 at 12:36 PM Andy Sayer <andysayer_at_gmail.com<mailto:andysayer_at_gmail.com><mailto:andysayer_at_gmail.com<mailto:andysayer_at_gmail.com>>> wrote: Yes, you can do it parallel (and in this circumstance it’s parallel query + parallel DDL) and online. The main difference is that your reading of the table can’t use direct path reads when it’s online.
If you can’t see parallel sessions being used then it’s likely because there weren’t any free to be used. If you have diagnostic+tuning pack licenced you can run the query on the bottom of https://ctandrewsayer.wordpress.com/2017/10/19/how-many-rows-were-insertedupdateddeleted-in-my-merge/ against the sql_id to see the reported reason for DOP downgrade.
That said, direct path read for parallel query on a partitioned table won’t necessarily happen anyway due to some bugs that have only recently been addressed.
Hope that helps,
Andrew
-- http://www.freelists.org/webpage/oracle-lReceived on Fri Sep 14 2018 - 08:53:28 CEST